http://www.lloydianaspects.co.uk/weapons/spear.html

There are many writers who insist that spears were used over-arm. I believe these writers to be wrong. The pictorial evidence is very poor. Where spears are shown to be used over-arm, it seems that this is for dramatic effect rather than for authenticity. Archaeology will tell us nothing on this issue, and I have come across no written record from antiquity which strongly backs up the over-arm theory. I shall now present my case for the under-arm use of spears.
The OP here had a valid point, and all I see addressing it are a bunch of mindless parrots claiming a "huge amount of ancient art" they've never personally looked at as corroborating evidence. The sense I get is that you all think "it's right because that's how the EB devs did it".